This invention relates to foil-covered plastic parts and method of making such parts and, in particular, to foil-covered automotive interior plastic parts having a decorative preform and methods of making such automotive interior plastic parts utilizing a hot stamping machine.
Typically, automotive interior plastic parts are painted after they are molded. The painting process requires elaborate facilities and consequently necessitates large expenses. For instance, significant square footage of a factory must be dedicated to a clean room environment for the spraying of paint and clear coat and for the baking and curing of paint on components, such as those components used in the automotive industry, such as body panels, air bag covers, instrument panels and the like. Moreover, solvent-based paints have in recent years raised significant environmental concerns because of the volatile organic components which are emitted into the air during the application of such solvent-based paints. As a result, the evaporation of such solvents must be strictly monitored to satisfy environmental and safety regulations.
In addition, automotive components, especially interior automotive components, are strictly scrutinized following the painting process in order to match or conform the automotive component to the styling and aesthetic requirements of the associated interior trim product. Painting such automotive components following the molding process, raises quality concerns with respect to the color, consistency, and thickness of each individual paint application.
U.S. Pat. No. 5,678,851 to Saito et al. discloses an air bag module cover including an ornament on a cover member. The ornament may be made from a resin material with a metal foil.
U.S. Pat. No. 4,902,557, the Rohrbacher reference discloses a method and apparatus for manufacturing a thermoplastic polyolefin composite useful as an exterior auto or truck body part.
U.S. Pat. No. 4,769,100, the Short reference, teaches a method of applying a carrier film pre-printed with metallic paint to an automobile body panel in a vacuum forming process.
U.S. Pat. Nos. 4,952,351 and 5,466,412, the Parker patents, teach a method of manufacturing an air bag cover for an inflatable air bag system including a bondable film carrier, which is painted after the film carrier is molded.
Hot stamping is utilized for plastic decorating. For example, U.S. Pat. No. 5,769,548 discloses a hot stamp imprinting system with latchable ink ribbon cassette and handle.
Presently, when air bag covers are provided in automobiles on the driver""s side of the vehicle, the air bag is stored in the steering column behind an air bag cover. During automatic inflation of the air bag, the air bag cover moves away from the steering column to permit its safety function between the steering column and the operator of the vehicle.
Recent practice in the automotive industry is utilization of all plastic fabricated air bag covers. It is known in other automotive parts areas that different, aesthetically pleasing outer surfaces enhance the overall appearance of the interior of automotive vehicles. Use of decorative appliques having solid colors contrasting or blending with the different colors of the plastic air bag covers is often sought after. Simulated wood grain finishes, and metallic finishes are also popular and economically feasible in combination with various plastic automotive parts.
Difficulties are known to arise in properly applying applique films to annular or arcuate plastic outer surfaces. Applique films are usually approximately 0.5 millimeters thick or less and are therefore not easily applied directly to an outer air bag cover surface. Improper application causes small air pockets to occur on the decorative film which often makes the resultant air bag cover, unattractive and thus unusable. Additionally, conventional air bag covers invariably include annular or arcuate surfaces, and affixing the thin applique film to these designated surfaces is even more difficult.
The deposition or fastening of the applique must be perfected with a method that affords a smooth surface and neat appearance. Thus it is known to utilize a backing material or liner in conjunction with a thin applique film to afford a clean, smooth appearance of the final product.
In addition, the applique must be affixed to the front cover in such a way as to prevent the applique from separating from the front cover when the air bag deploys. The applique must therefore be bonded to the front cover with sufficient strength to prevent fragmentation of the applique during air bag inflation and exit.
The U.S. patents to Eckout U.S. Pat. Nos. 5,487,557 and 5,529,336 disclose an automotive air bag cover having a decorative applique fastened thereto. The air bag cover is manufactured from plastic and includes a front panel adapted to enclose an uninflated automotive air bag. The front panel includes inner and outer surfaces. Side panels are further provided and are connected to and extend from the front panel. The decorative applique is fastened to the outer surface of the front cover by a plurality of connecting towers which extend through the front cover. Seams are provided for permitting the air bag to inflate and exit the front cover. The decorative applique is fastened to the front cover adjacent the seams in a non-overlapping fashion such that the decorative applique does not interfere with exit or inflation of the air bag.
However, the prior art fails to provide a foil-covered automotive interior plastic part having a decorative preform and method of making same wherein hot stamping is used and wherein the foil is bonded to a substrate of the plastic part so as to have the durability and strength necessary to support varying applications yet comply with styling and aesthetic requirements.
An object of the present invention is to provide a foil-covered automotive interior plastic part and method of making same wherein a decorative preform in combination with at least one foiled decorative feature formed on an outer surface of a plastic structural substance of the plastic part present an aesthetically pleasing appearance.
In carrying out the above object and other objects of the present invention, a foil-covered automotive interior plastic part is provided. The foil-covered plastic part includes a plastic structural substrate including at least one foil-receiving portion formed on an outer surface thereof and a decorative preform bonded to the outer surface in non-overlapping fashion with respect to the at least one foil-receiving portion. The foil-covered plastic part also includes a hot stamping foil having a foil top layer disposed on a plastic bottom layer which, in turn, is bonded to an outer surface of the at least one foil-receiving portion to form the automotive interior foil-covered plastic part. The resulting part has an aesthetically pleasing appearance.
The at least one foil-receiving portion may include a plurality of raised design portions having top and side surfaces.
The decorative preform may include a plurality of apertures extending between front and rear surfaces of the preform at predetermined spaced locations. The raised design portions extend through the corresponding apertures. The foil layer completely covers the top surfaces and the side surfaces of the raised design portions which extend above the front surfaces of the preform.
The raised design portions may represent screw heads.
The decorative preform preferably comprises a plastic film sheet compatible with the plastic of the substrate so that diffusion occurs between the plastic film sheet and the outer surface of the substrate. The plastic film sheet is shaped correspondingly to the outer surface of the substrate.
The plastic layer of the hot stamping foil is preferably compatible with the at least one foil-receiving portion so that diffusion occurs therebetween.
In one embodiment, the foil layer is a chrome layer.
In the embodiment shown, the substrate is a plastic front panel of an automotive air bag cover adapted to enclose an uninflated automotive air bag.
Still further in carrying out the above object and other objects of the present invention, a method is provided for making the foil-covered automotive interior plastic part. The method includes providing a film sheet, vacuum molding the film sheet in a mold cavity to obtain a decorative preform having plastic top and bottom surfaces, and placing the decorative preform in a mold cavity of an injection mold having a shape defining the part. The method also includes injecting a thermoplastic elastomer into the mold cavity of the injection mold to generate a substrate of the part wherein the generation of the substrate of the part creates sufficient pressure and heat to bond the substrate to the bottom surface of the decorative preform and to form at least one foil-receiving portion at a top surface of the substrate which does not overlap with the preform. The method also includes the steps of providing a hot stamping foil having a foil top layer disposed on a plastic bottom layer, aligning the hot stamping foil with the at least one foil-receiving portion in a hot stamping machine, and operating the hot stamping machine for a time sufficient to generate a temperature and a pressure sufficient to melt and combine a top surface of the at least one foil-receiving portion and the plastic bottom layer of the hot stamping foil to form the foil-covered automotive interior plastic part.
Important advantages of hot stamping are:
Dry Decorating Methodxe2x80x94A hot stamped part is immediately ready for handling and packaging.
Variety of Materialsxe2x80x94A variety of materials can be decorated using the hot stamping process. The most commonly decorated material is thermoplastics, but thermosets as well as wood, book cloth, leather, textiles, paper, cardboard and pre-painted metals are stamped with great success.
Variety of Decorating Finishesxe2x80x94Hot stamping is a decorative method where permanent gold and silver metallic graphics can be produced. Foils are also manufactured in gloss or matte pigment colors, wood grain designs, brushed effects, and chromium for exterior use. Multi-colored graphics can also be accomplished with pre-printed heat transfers and continuous patterned foils.
Variety of Surface Geometriesxe2x80x94Hot stamp foils can be applied to a variety of surface geometries including flat, cylindrical and spherical shaped parts along with raised beads graphics.
Minimum Set-Up Timexe2x80x94To change the stamping color simply involves changing a dry roll of hot stamp foil.
Permanent Decorationxe2x80x94Hot stamping foil has excellent adhesion and abrasion resistance due to thermal bonding that takes place.
EPA or Fire Safety Considerationsxe2x80x94With hot stamping, there are no EPA or fire safety considerations to be concerned about. Hot stamping, unlike other decorating methods, does not require any special storage, insurance or removal of hazardous solvents or vapors.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.